All my previous builds have had race tracks with cup holders in the wood. This time I wanted to try cupholders in the rail and get rid of the race track. I was concerned that the sharp edges of the cupholders would wear the vinyl over time and cut through eventually. So I decided to use O-rings as a barrier between the cup lip and the vinyl. Pics below with the part number for jumbo size. I think they look good, I rounded the wooden rings with 3/8” router bit so the o-rings would sink further down into hole. Happy building!